Roger Sterling has done many, many things in his time. He has run an ad agency (occasionally into the ground), survived several heart attacks, dropped acid, fathered a son with a co-worker, and drunk an ocean of scotch.

But what he really wants to do is direct.

At least the man who plays Roger does, and you’re forgiven if you mistake one for the other.

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John Slattery, son of Boston, has made such an impact as Roger Sterling over seven seasons of “Mad Men” that it’s easy to assume the actor is the role. For one thing, Roger is absurdly, maliciously entertaining, as he says what all the other characters on AMC’s hit series dare not.

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For another, he has evolved over the show’s long haul from the entitled jester of the Sterling Cooper ad agency to a movingly flawed (if ever charming) survivor of the ’60s culture wars. That’s a testament to the skills of the man playing him.

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Those skills have now circled behind the camera. Slattery, 51, moved into the director’s chair during the fourth season of “Mad Men” and has helmed five episodes to date. With the release of “God’s Pocket,” an adaptation of Pete Dexter’s 1983 novel about the denizens of a gritty South Philadelphia enclave, Slattery makes his feature film directorial debut. (The film opened last Friday in New York and Los Angeles and comes to Boston Friday.)

Set during the late 1970s, “God’s Pocket” is a far cry from the bon vivant capers of Roger Sterling. An ensemble piece shot through with the pitch-black comedy of Murphy’s Law in action, it centers on Mickey Scarpato, played by Philip Seymour Hoffman in one of the much-loved actor’s final roles before his Feb. 2 death from a drug overdose.

A small-time crook and neighborhood kingpin, Mickey spends most of the film coping with the murder of his stepson (Caleb Landry Jones), a budding sociopath mourned by no one but his mother, Mickey’s wife, Jeanie (Christina Hendricks of “Mad Men”).

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Things fall mordantly and consistently apart, to the point where Mickey is forced to tote the stepson’s body around in his refrigerated meat truck. The film’s cast is a rogue’s gallery of indie-film stalwarts that includes John Turturro (as Mickey’s partner in crime), Richard Jenkins (as an alcoholic newspaperman), and Eddie Marsan (as a penny-pinching mortician).

The one person you won’t see up on the screen is John Slattery. The man has something to prove.

What that may be takes some time to reveal itself.

“I didn’t really think of myself as being in it,” Slattery says, recalling the experience of reading Dexter’s novel years ago. “I closed the book and thought of it as a film. It was that simple.

“That black sense of humor is what got me, and those characters who were prepared to do whatever they had to do while not losing their sense of humor. The casual violence of the place, which to me meant funny. And the details were so specific and visual. Everything was fully formed.”

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Slattery is sitting in a trendy gastropub off Broadway in Manhattan’s high twenties, congenial if slightly distracted by the day’s PR duties for “God’s Pocket.” He’s more thoughtful than his “Mad Men” counterpart — maybe it’s the black-framed glasses — and less compulsively put together, with a crisp pink-and-blue plaid shirt offset by white hair mussed in un-Rogerly fashion.

He has just come from doing NPR’s “All Things Considered,” he has a photo shoot in an hour, and right now all he wants is a hamburger. The menu’s not playing along: A high-end lamb burger doesn’t cut it. He settles for the fried fluke and chips and sips the first of two microbrews.

The ensuing conversation encompasses Slattery’s growing pains as a director and his experience working with Hoffman, but it begins where Slattery began, in the suburbs of Newton and Wellesley, where the future actor was the fifth of six children in the family scrum of leather merchant Jack Slattery and his wife, Joan.

“I grew up in Auburndale, on the corner of Vista and Aspen Avenue,” says John Slattery. “Right across from the 17th hole of the Woodland Golf Club. I used to caddie there.”

He was schooled at the finer Catholic institutions of Newton — Mount Alvernia for elementary, Saint Sebastian’s (now in Needham) for high school — with a stint at Wellesley Junior High after the Slatterys moved one town over.

He was a ballplayer rather than a theater kid, and his interest in acting came more from the movies he obsessively absorbed on TV and in neighborhood theaters: “I remember ‘Butch Cassidy’ first-run, I remember ‘The Great Waldo Pepper’ in that Wellesley movie theater on the corner of Washington and Highland. You could get in for a buck or a solid silver quarter. I would watch late-night stuff, Cary Grant, ‘The Godfather,’ comedies, ‘The Omen.’ Seeing those movies was . . . big.”

So was Mr. Mitchell, an English teacher at Wellesley Junior High (now Wellesley Middle School) who imparted lessons in grammar, Bob Dylan lyrics, and social justice, and whom Slattery recalls as a major influence in broadening his horizons.

“He flipped the switch, so that I picked my head up and looked around more,’’ Slattery said. “He was critical, he was smart and funny and out there. Someone just brought his name up, and I’d love to know what happened to him.”

Peter Mitchell’s doing just fine, thank you. Reached by phone at his home in Wellesley, the now-retired teacher, 64, remembers his former pupil well. “Slattery!” he says. “I can still see him, literally, this little blond-haired character in the fourth row, third seat, in a sports jacket. He was a teacher’s dream, very inquisitive, open to talking about things.”

That early curiosity, coupled with his fascination with movies, pushed Slattery toward acting when he landed at Catholic University in Washington, and it propelled him to New York in the mid-1980s, where he traveled the traditional actor’s path: horrible apartments, menial waiting jobs, and slow-gathering success onstage, on TV, and in films.

His natural poise, waspish way with dialogue, and prematurely gray hair combined to make him a go-to character actor for shows like “Sex and the City,” “Desperate Housewives,” and “Will & Grace,” and when the career-defining role of Roger Sterling came along in 2007, Slattery stepped into it as if it were a bespoke suit.

Slattery’s youthful movie-love may also partly explain his interest in getting behind the camera.

“Actors in general make pretty good directors, but they focus more on performance,” says “Mad Men” director Phil Abraham, who served as Slattery’s on-set mentor. “John surprised me in that his door into the scene is really as a filmmaker: How am I going to construct this, what is my coverage, let me do it in this great single moving shot. He’s creating a life with the camera in ways you don’t necessarily expect from an actor.”

Slattery shadowed Abraham through the process of prepping a “Mad Men” episode, including coming along to the show’s deserted set on weekends while the director worked out his shots. “I was pleased that he wanted to do that with me,” Abraham says, “and I could tell right away that he had an aptitude for it. I think he’s the real deal.”

But directing a TV episode — even one as densely constructed as “Mad Men” — is very different from tackling a feature film. “Network TV shows are there for the whole year,” Slattery explains. “The costumes are there, the sets are there, the actors are there, so if you screw something up, you can go back and get it. But ‘God’s Pocket’ was a period film with 40 people and 28 locations in 24 days.

“You can block off a street for four hours to shoot a sequence that looks like 1978 until all of a sudden you have minivans driving through and it doesn’t look like 1978 anymore. It’s gone. And you have to make creative decisions under that pressure.”

It helps if you trust your actors and they trust you. The upside of Slattery’s long resume is that the “God’s Pocket” cast knew him as a peer. Besides, they were thrilled to be working with Hoffman, who brought a unique, embattled charisma to his role.

Mickey Scarpato is the unoffical mayor of his 10 square blocks, and he makes a decent living in meats and other goods that happen to fall off the back of trucks, but he has been staving off defeat for years — everyone else in God’s Pocket appears to have already thrown in the towel — and the bleak farce of the film’s events finally threatens to bring him down. That knowledge of disaster is written in every scene on Hoffman’s exhausted, astounded face.

“What made [Hoffman] special was him,” Slattery says. “He had a face and a voice and a body and an ability to use all of them, and a technical wherewithal that was amazing. I was always surprised that he could be deeply emotionally involved in a scene and yet aware of where the camera was. Just when you’d think, ‘I wish he would turn,’ he would turn.”

The two were collegial but not close before production on “God’s Pocket” began in June 2013. A month earlier, Hoffman had checked himself into rehab; after years of sobriety, he had started using drugs again.

Slattery says he saw no evidence of the actor’s struggles. “He’d show up for work and do things that would make you shake your head and think, ‘There’s no one else I know who can do that,’ and then he’d leave. And I would continue on with the eight million other things I had to do.”

The two last met at the Sundance Film Festival in January, when “God’s Pocket” premiered to a capacity crowd. “He was fantastic and funny and positive,” Slattery recalls. “One of the things I’m very glad about is how pleased he was with the film. Because it becomes my job to sell it, and I know I’m selling something he was proud of.”

The filmmaker — for that’s what Slattery is now — can be proud, too. Despite a friendly reserve in conversation, you can tell the man is jazzed by his career change. Like many actors, he’s resistant to discussing the mystery of what he does, because to articulate the process is to start to ruin it.

When the talk turns to directing, though, Slattery perks up. He speaks more quickly; the ideas come piling out.

Maybe this is Mr. Mitchell’s inquisitive kid pushing again into new territory, just as he once lifted his head to look beyond the borders of the western suburbs. Or maybe this is just John Slattery’s way of reminding himself — and us — that there’s more to him than Roger Sterling, and that there’s much more yet to come.